The use of Serratia marcescens bacteriophage as a tracer and a model for virus removal in the Cayman Islands' waste stabilisation ponds was investigated. A series of bench-scale experiments was designed and carried out to determine the survival of Serratia marcescens bacteriophage in the various stages of a waste stabilisation pond system. The study investigated whether the physico-chemical conditions expected in facultative and maturation ponds precluded the use of phage tracers. By the end of the 6th day, phage in filtered and unfiltered raw sewage and facultative pond samples, in normal sunlight, was undetectable. In the maturation pond samples, in normal sunlight, phage was undetectable by the 4th day. There was a high correlation between increased phage reduction and increased pH levels. The phage was still detectable on day 13 in maturation pond experiments kept in the dark. Therefore the study concluded that Serratia marcescens bacteriophage may be useful as a tracer in ponds with retention times up to 14 days provided average pH at the outlet is <9.0.

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